The objectives of this Program Project Grant are illustrated broadly by its title: "A Research and Resource Program in Blood" and more precisely by the titles of each project which have been arranged in five study groups, each an area of research which is of concern in the Blood Banking Sciences and which affect directly or indirectly, the problems of blood transfusion. I. Studies in Genetics and Immunology: 1. "Genetic Markers in Human Blood and Gene Mapping". 2. "Theoretical Population Genetics". 3. "A Multifaceted Program for the Study of Chromosome Change in Human Diseases". II. Studies in Hepatitis: 4. Characterization of Hepatitis B Antigen Particles. 5. The epidemiology of Viral hepatitis Types A, B and Non-A, Non-B in Normal Populations. 6. The Prevention of B and Non B Viral Hepatitis". 7. Characterization of hepatitis Viruses and Development of Screening Tests. III. Plasma Proteins: Structure, Biosynthesis and Secretion: 8. Biosynthesis of Fibrinogen. 9. The Regulation of Synthesis and Transport of Diverse Proteins in Liver. IV. Regulatory Mechanisms in Nucleic Acid Metabolism: 10. Control of RNA Synthesis in Nucleated Cells.